In Figure 1, they assess the degree to which Aplysia CNS extract specifically binds to CRE of a rat somatostatin gene in order to determine whether or not Aplysia contains a CREBP-like protein. Fragments of DNA not bound to proteins run faster down the gel, allowing researchers to determine whether or not the DNA present has associated proteins (see tip on gel mobility shift assays above). In this case, binding of CRE to DNA fragments from Aplysia CNS extract would indicate presence of a CREBP-like protein in Aplysia CNS. The first part of the figure represents a gel mobility shift assay that shows three retarded bands corresponding to a similar finding when a CRE probe from the vasoactive intestinal protein was used. In part B of the figure, they use two AP-1 sequences, each differing from the CRE sequence by only one nucleotide, to show that binding of Aplysia proteins to somatostatin CRE is sequence-specific. Overall, this figure confirms that Aplysia CNS extract contains a CREBP-like protein by showing sequence-specific binding of the Aplysia CNS extract to the CRE of a rat somatostatin gene.